11/2018
Copyright © 2018
Campbell Scientific, Inc.
Limited Warranty
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the sole and exclusive remedy under this warranty. The Customer assumes all costs of removing,
reinstalling, and shipping defective Products to CSI. CSI will return such Products by surface car-
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such Products best way CIP (port of entry) per Incoterms ® 2010. This warranty shall not apply to
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Assistance
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Safety
DANGER — MANY HAZARDS ARE ASSOCIATED WITH INSTALLING, USING, MAINTAINING, AND WORKING ON OR AROUND TRIPODS,
TOWERS, AND ANY ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS, CROSSARMS, ENCLOSURES, ANTENNAS, ETC. FAILURE
TO PROPERLY AND COMPLETELY ASSEMBLE, INSTALL, OPERATE, USE, AND MAINTAIN TRIPODS, TOWERS, AND ATTACHMENTS, AND
FAILURE TO HEED WARNINGS, INCREASES THE RISK OF DEATH, ACCIDENT, SERIOUS INJURY, PROPERTY DAMAGE, AND PRODUCT FAILURE.
TAKE ALL REASONABLE PRECAUTIONS TO AVOID THESE HAZARDS. CHECK WITH YOUR ORGANIZATION'S SAFETY COORDINATOR (OR
POLICY) FOR PROCEDURES AND REQUIRED PROTECTIVE EQUIPMENT PRIOR TO PERFORMING ANY WORK.
Use tripods, towers, and attachments to tripods and towers only for purposes for which they are designed. Do not exceed design limits. Be
familiar and comply with all instructions provided in product manuals. Manuals are available at www.campbellsci.com or by telephoning
(435) 227-9000 (USA). You are responsible for conformance with governing codes and regulations, including safety regulations, and the
integrity and location of structures or land to which towers, tripods, and any attachments are attached. Installation sites should be evaluated
and approved by a qualified engineer. If questions or concerns arise regarding installation, use, or maintenance of tripods, towers, attach-
ments, or electrical connections, consult with a licensed and qualified engineer or electrician.
General
l Prior to performing site or installation work, obtain required approvals and permits. Comply with all governing structure-height reg-
ulations, such as those of the FAA in the USA.
l Use only qualified personnel for installation, use, and maintenance of tripods and towers, and any attachments to tripods and
towers. The use of licensed and qualified contractors is highly recommended.
l Read all applicable instructions carefully and understand procedures thoroughly before beginning work.
l Wear a hardhat and eye protection, and take other appropriate safety precautions while working on or around tripods and towers.
l Do not climb tripods or towers at any time, and prohibit climbing by other persons. Take reasonable precautions to secure tripod
and tower sites from trespassers.
l Use only manufacturer recommended parts, materials, and tools.
Utility and Electrical
l You can be killed or sustain serious bodily injury if the tripod, tower, or attachments you are installing, constructing, using, or main-
taining, or a tool, stake, or anchor, come in contact with overhead or underground utility lines.
l Maintain a distance of at least one-and-one-half times structure height, 20 feet, or the distance required by applicable law,
whichever is greater, between overhead utility lines and the structure (tripod, tower, attachments, or tools).
l Prior to performing site or installation work, inform all utility companies and have all underground utilities marked.
l Comply with all electrical codes. Electrical equipment and related grounding devices should be installed by a licensed and qualified
electrician.
Elevated Work and Weather
l Exercise extreme caution when performing elevated work.
l Use appropriate equipment and safety practices.
l During installation and maintenance, keep tower and tripod sites clear of un-trained or non-essential personnel. Take precautions to
prevent elevated tools and objects from dropping.
l Do not perform any work in inclement weather, including wind, rain, snow, lightning, etc.
Maintenance
l Periodically (at least yearly) check for wear and damage, including corrosion, stress cracks, frayed cables, loose cable clamps, cable
tightness, etc. and take necessary corrective actions.
l Periodically (at least yearly) check electrical ground connections.
WHILE EVERY ATTEMPT IS MADE TO EMBODY THE HIGHEST DEGREE OF SAFETY IN ALL CAMPBELL SCIENTIFIC PRODUCTS, THE CUSTOMER
ASSUMES ALL RISK FROM ANY INJURY RESULTING FROM IMPROPER INSTALLATION, USE, OR MAINTENANCE OF TRIPODS, TOWERS, OR
ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS, CROSSARMS, ENCLOSURES, ANTENNAS, ETC.
1. SR20-D2 introduction
The SR20-D2, manufactured by Hukseflux Thermal Sensors, is an ISO 9060 digital secondary-
standard pyranometer that measures solar short-wave radiation in a full hemisphere of the sky. It
has a built-in case-temperature sensor and embedded heater for removing dew and light rain. It
connects directly to Campbell Scientific data loggers and is designed for applications that require
high measurement accuracy in demanding applications such as scientific meteorological obser-
vation networks and utility scale solar-energy-power production sites.
2. Installation
2.1 Siting
The solar radiation sensor is usually installed horizontally, but can also be installed at any angle
including an inverted position. Site the sensor to allow easy access for maintenance while ideally
avoiding any obstructions or reflections above the plane of the sensing element. It is important
to mount the sensor such that a shadow or a reflection will not be cast on it at any time.
If this is not possible, try to choose a site where any obstruction over the azimuth range between
earliest sunrise and latest sunset has an elevation not exceeding 5°. Diffuse solar radiation is less
influenced by obstructions near the horizon. The sensor should be mounted with the cable point-
ing towards the nearest magnetic pole. For example, in the northern hemisphere, point the cable
toward the North Pole.
2.2 Mounting procedure
1. On a level surface, level the solar radiation sensor using the leveling feet on the sensor.
Alternatively, remove the sensor leveling feet to allow it to be mounted directly to the
mounting bracket.
2. Secure the solar radiation sensor to the mounting bracket. The blue dots in the following
figure indicate the mounting holes used for this pyranometer.
SR20-D2 ISO Secondary Standard Pyranometer 1
3. Using a diopter in combination with a solar compass, install and orient the crossarm on the
tripod or the mast. If installing the mounting bracket on a vertical pole, ensure the pole is
truly vertical.
4. Secure the mounting bracket to the crossarm or vertical pole using the hardware included
with the mounting bracket. The CM255 uses one U-bolt, nuts, flat washers, and lock wash-
ers to mount the bracket, as shown in the following figure.
5. For the CM255LS bracket, use the two set screws to secure the bracket to the crossarm or
pole as shown in the following figure. For pyranometers mounted horizontally, ensure the
mounting bracket is horizontal in two dimensions. For pyranometers mounted at an angle,
SR20-D2 ISO Secondary Standard Pyranometer 2
set the mounting bracket angle to the desired angle prior to tightening the mounting hard-
ware.
6. Verify mounting hardware is firmly tightened, and that the mounting bracket is at the
desired angle. The CM255LS includes leveling bolts for additional adjustment of the pyrano-
meter level.
3. SR20-D2 wiring
Table 3-1: Pin-out, wire color, function, and data logger connection
Wire color
Pin out
Function Data logger connection
-PT -PW
Green 5 2 RS-485A A-, C (odd)
White 7 4 RS-485B B+, C (even)
Red 2 1 Power in (12 V) 12V
Black 6 3 Power ground G
Clear 9 5 Shield ⏚ (analog ground)
1
Assumes the sensor directly connects to the data logger.
SR20-D2 ISO Secondary Standard Pyranometer 3
3. RS-485 default configuration
The default RS-485 settings are: 19200 baud rate, 8 data bits, even parity, one stop bit. This con-
figuration is used for most Modbus networks.
4. SR20-D2 register map
Table 4-1 (p. 4) provides the register map for the most commonly used values. A comprehensive
register map is available in the Hukseflux manual.
Table 4-1: RS-485 register map
Starting
Register
Number
Register
Count
Data Format Units Description
1 1 Signed 16 bit integer Modbus address
3 2 Signed32bitinteger mW/m
2
Irradiance (temperature
compensated signal)
5 2 Signed32bitinteger mW/m
2
Irradiance (temperature
uncompensated signal)
7 1 Signed 16 bit integer 0.01 °C Sensor body temperature
8 1 Signed 16 bit integer x 0.1 Ω Sensor electrical resistance
9 1 Signed 16 bit integer Scaling factor irradiance
10 1 Signed 16 bit integer Scaling factor temperature
11 2 Signed 32 bit integer nV Sensor voltage output
41 1 Signed 16 bit integer Serial number
42 2 Float µV/W/m
2
Sensor sensitivity
47 2 Signed 32 bit integer Calibration date
99 1 Signed 16 bit integer x 0.01 % Humidity
SR20-D2 ISO Secondary Standard Pyranometer 4
5. RS-485 programming
The RS-485 output can be directly read by a MeteoPV, CR6-series, CR1000X-series, or Modbus
RTU RS-485 network. Other Campbell Scientific data loggers can use an MD485 multidrop inter-
face to read the RS-485 output. Refer to the MD485 manual for information about using the
MD485.
A CR6 or CR1000X data logger programmed as a Modbus Master can retrieve the values stored in
the Input Registers. To do this, the CRBasic program requires a SerialOpen() instruction fol-
lowed by the ModbusMaster() instruction.
The SerialOpen instruction has the following syntax:
SerialOpen (ComPort, Baud, Format, TXDelay, BufferSize, Mode)
The Format is typically set to logic 1 low; even parity, one stop bit, 8 data bits. The Mode
parameter should configure the ComPort as RS-485 half-duplex, transparent. The
ModbusMaster() instruction has the following syntax:
ModbusMaster (Result, ComPort, Baud, Addr, Function, Variable, Start, Length,
Tries, TimeOut, [ModbusOption])
The Addr parameter must match the sensor Modbus address. To collect all of the values, the
Start parameter needs to be 1 and the Length parameter needs to correspond with the
sensor type (see SR20-D2 register map (p. 4)). ModbusOption is an optional parameter
described in the CRBasic Editor Help. Refer to example program section for more information.
6. SR20-D2 example program
Table 6-1: Wiring for example program
Wire color Function Data logger connection
Green RS-485A C5
White RS-485B C6
Red Power in (12 V) 12V
SR20-D2 ISO Secondary Standard Pyranometer 5
Table 6-1: Wiring for example program
Wire color Function Data logger connection
Black Power ground G
Clear Shield ⏚ (analog ground)
CRBasic Example 1: CR1000X program for measuring the SR20-D2
'CR1000X Series Datalogger
'Hukseflux SR20-D2 Pyranometer
'SR20 is a ISO 9060 Secondary Standard digital pyranometer
'D2 uses Modbus RS-485 protocol
'PN 34088 SR20-D2CBL-L (CSI's SR20D2 Cable)
Dim SR20D2(15) As Long
Public SR20D2_IRR_TC 'Temperature compensated x 0.01 W/M^2
Public SR20D2_IRR 'Uncompensated x 0.01 W/M^2
Public SR20D2_BodyTemp As Float
Public SR20D2_SerialNumber As Float
Public SR20D2_CalDate As Long
Public SR20D2_Humidity As Float
Public SR20D2_ScaleFactor_IRR As Long
Public SR20D2_ScaleFactor_BodyTemp As Long
Public SR20D2_ElecResistance As Long
Public SR20D2_VoltageOut As Float
Public ModbusResult_IRR_TC
Public ModbusResult_IRR
Public ModbusResult_BodyTemp
Public ModbusResult_SN
Public ModbusResult_CalDate
Public ModbusResult_Humidity
Public ModbusResult_SFIRR
Public ModbusResult_SRTemp
Public ModbusResult_ElecRes
Public ModbusResult_VoltOut
Units SR20D2_IRR = W/m^2
Units SR20D2_IRR_TC = W/m^2
Units SR20D2_BodyTemp = DegC
Units SR20D2_Humidity = %
Units SR20D2_ElecResistance = Ohm
Units SR20D2_VoltageOut = uV
DataTable (OneMin,1,-1)
DataInterval (0,1,Min,10)
Average (1,SR20D2_IRR,IEEE4,False)
Average (1,SR20D2_IRR_TC,IEEE4,False)
Maximum (1,SR20D2_IRR_TC,IEEE4,False,False)
Minimum (1,SR20D2_IRR_TC,IEEE4,False,False)
SR20-D2 ISO Secondary Standard Pyranometer 6
CRBasic Example 1: CR1000X program for measuring the SR20-D2
StdDev (1,SR20D2_IRR_TC,IEEE4,False)
Average (1,SR20D2_BodyTemp,IEEE4,False)
EndTable
DataTable (SR20D2_MetaData,1,-1)
Sample (1,SR20D2_ElecResistance,IEEE4)
Sample (1,SR20D2_VoltageOut,IEEE4)
Sample (1,SR20D2_Humidity,IEEE4)
EndTable
DataTable (SR20D2_SensorID,1,100)
Sample (1,SR20D2_SerialNumber,FP2)
Sample (1,SR20D2_CalDate,Long)
Sample (1,SR20D2_ScaleFactor_IRR,FP2)
Sample (1,SR20D2_ScaleFactor_BodyTemp,FP2)
EndTable
BeginProg
SerialOpen (ComC5,19200,2,0,50,4)
ModbusMaster (ModbusResult_SN,ComC5,19200,53,4,SR20D2(1),41,1,1,100,3)
'Serial Number
SR20D2_SerialNumber = SR20D2(1)
ModbusMaster (ModbusResult_CalDate,ComC5,19200,53,4,SR20D2(2),47,1,1,100,2)
'Cal Date
SR20D2_CalDate = SR20D2(2)
ModbusMaster (ModbusResult_SFIRR,ComC5,19200,53,4,SR20D2(3),9,1,1,100,3)
'Scaling Factor IRR
SR20D2_ScaleFactor_IRR = SR20D2(3)
ModbusMaster (ModbusResult_SRTemp,ComC5,19200,53,4,SR20D2(4),10,1,1,100,3)
'Scaling Factor Temp
SR20D2_ScaleFactor_BodyTemp = SR20D2(4)
ModbusMaster (ModbusResult_ElecRes,ComC5,19200,53,4,SR20D2(10), _
8,1,1,100,1)
'Electrical Resistance
SR20D2_ElecResistance = SR20D2(10)/10
ModbusMaster (ModbusResult_VoltOut,ComC5,19200,53,4,SR20D2(11), _
11,2,1,100,2)
'Voltage output
SR20D2_VoltageOut = SR20D2(11)
ModbusMaster (ModbusResult_Humidity,ComC5,19200,53,4,SR20D2(13),99,1,1,100,3)
'Humidity
SR20D2_Humidity = SR20D2(13)/100
Scan (1,Sec,0,0)
ModbusMaster (ModbusResult_IRR_TC,ComC5,19200,53,4,SR20D2(5),3,2,1,100,2)
'Irradiance temperature compensated
SR20D2_IRR_TC = SR20D2(5)/SR20D2_ScaleFactor_IRR
ModbusMaster (ModbusResult_IRR,ComC5,19200,53,4,SR20D2(7),5,2,1,100,2)
'Irradiance uncompensated
SR20D2_IRR = SR20D2(7)/SR20D2_ScaleFactor_IRR
ModbusMaster (ModbusResult_BodyTemp,ComC5,19200,53,4,SR20D2(9),7,1,1,100,1)
SR20-D2 ISO Secondary Standard Pyranometer 7
CRBasic Example 1: CR1000X program for measuring the SR20-D2
'Body Temp
SR20D2_BodyTemp = SR20D2(9)/SR20D2_ScaleFactor_BodyTemp
CallTable OneMin
NextScan
SlowSequence
Scan (6,Hr,0,0)
ModbusMaster (ModbusResult_ElecRes,ComC5,19200,53,4,SR20D2(10),8,1,1,100,1)
'Electrical Resistance
SR20D2_ElecResistance = SR20D2(10)/10
ModbusMaster (ModbusResult_VoltOut,ComC5,19200,53,4,SR20D2(11), _
11,2,1,100,2)
'Voltage output
SR20D2_VoltageOut = SR20D2(11)
ModbusMaster (ModbusResult_Humidity,ComC5,19200,53,4,SR20D2(13), _
99,1,1,100,3)
'Humidity
SR20D2_Humidity = SR20D2(13)/100
CallTable SR20D2_MetaData
NextScan
SlowSequence
Scan (1,Sec,0,1)
If SR20D2_SerialNumber = 0 Then
ModbusMaster (ModbusResult_SN,ComC5,19200,53,4,SR20D2(1),41,1,1,100,3)
'Serial Number
SR20D2_SerialNumber = SR20D2(1)
ModbusMaster (ModbusResult_CalDate,ComC5,19200,53,4,SR20D2(2), _
47,1,1,100,2)
'Cal Date
SR20D2_CalDate = SR20D2(2)
ModbusMaster (ModbusResult_SFIRR,ComC5,19200,53,4,SR20D2(3),9,1,1,100,3)
'Scaling Factor IRR
SR20D2_ScaleFactor_IRR = SR20D2(3)
ModbusMaster (ModbusResult_SRTemp,ComC5,19200,53,4,SR20D2(4),10,1,1,100,3)
'Scaling Factor Temp
SR20D2_ScaleFactor_BodyTemp = SR20D2(4)
ModbusMaster (ModbusResult_ElecRes,ComC5,19200,53,4,SR20D2(10), _
8,1,1,100,1)
'Electrical Resistance
SR20D2_ElecResistance = SR20D2(10)/10
ModbusMaster (ModbusResult_VoltOut,ComC5,19200,53,4,SR20D2(11), _
11,2,1,100,2)
'Voltage output
SR20D2_VoltageOut = SR20D2(11)
ModbusMaster (ModbusResult_Humidity,ComC5,19200,53,4,SR20D2(13), _
99,1,1,100,3)
'Humidity
SR20D2_Humidity = SR20D2(13)/100
SR20-D2 ISO Secondary Standard Pyranometer 8
CRBasic Example 1: CR1000X program for measuring the SR20-D2
EndIf
CallTable SR20D2_SensorID
NextScan
EndProg
7. Maintenance and
troubleshooting
The pyranometer has no service items requiring scheduled replacement. There is no accessible
desiccant cartridge to maintain. Use pure alcohol or distilled water and a lint-free cloth to clean
the dome, ensuring no smears or deposits are left on the dome. Local conditions and application
dictate cleaning interval. Sophisticated research applications require daily cleaning. For typical
PV applications, clean once per week, bi-monthly, or monthly. The pyranometer should be recal-
ibrated following industry standard best practices such as ASTM G167, ISO 9846, ASTM E824 or
ASTM G207 by an accredited lab. The recommended recalibration interval is two years. Contact
Campbell Scientific for more information.
Unexpected results typically occur because of improper wiring or programming, electromagnetic
radiation, or damaged cables. Ensure that the data logger program includes the correct para-
meters for the measurement instructions. Check for the presence of strong sources of elec-
tromagnetic radiation and use the 50 or 60 Hz integration option in the data logger program if
electromagnetic radiation can be a problem. Check the cable for damage and ensure that it is
properly connected to the data logger.
SR20-D2 ISO Secondary Standard Pyranometer 9
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